AIX multibos mksysb migration

I’ve
written about multibos before, here and here. But recently I
started experimenting with multibos mksysb migration. A customer asked me how
this worked and apart from a high-level view I wasn’t able to provide any real
world experience, so I thought I’d give it a try. What follows is just a ‘brain
dump’ from my quick test.

First of all
this isn’t really a migration. It just simply populates a second instance of
AIX with a higher-version. It doesn’t really migrate (or merge) your existing
configuration into the second instance. So I’m not sure how useful this feature
really is right now.

Starting with
5.3 TL9 you can add a 6.1 TL2 (or above) instance. This is done with the new –M
flag. You must be running with the 64bit kernel.

This isn’t really a migration because it populates the second instance using a
mksysb based on the new release.

In 6.1 TL2 a new flag (-M) was added to the mksysb command which allows you to
create a mksysb for use with multibos. It creates a backup of BOS (/, /usr,
/var, /opt).
bos.alt_disk_install.boot_images must be installed.

It is not advised to run in this environment for an extended period of time.
There could be problems if tfactor or maps are used. Be aware that 6.1 specific
attributes may not be reflected in the standby instance.

So in my
lab environment I have two AIX LPARs. One is running AIX 6.1 and the other
running AIX 7.1.

First I
take a mksysb (with the –M flag) of the AIX 7.1 system to a file. This file
will be called by multibos to populate the second instance.

aix7[/] > mksysb -Mie /data/aix7-mksysb

Creating information file
(/image.data) for rootvg.

Creating list of files to back up.

Backing up 71643 files.....

71643 of 71643 files (100%)

0512-038 mksysb: Backup Completed
Successfully.

aix7[/] > ls -ltr /data

total 4276112

drwxr-xr-x2 rootsystem256 Feb 21 20:59
lost+found

-rw-r--r--1 rootsystem2189363200 Feb 21 21:06
aix7-mksysb

I copied this
file over to my AIX 6.1 system. This was the system that was to be ‘migrated’.
The next step was to perform a preview of the multibos operation.

Upon
checking my bootlist output, I
noticed (as expected) that the list now contained two extra entries for bos_hd5. These were the boot logical
volume entries for the second instance. If I was to boot from this LV I’d be
booting into AIX 7.1. Cool.

root@aix6 /# bootlist -m normal -o

hdisk0 blv=bos_hd5

hdisk0 blv=bos_hd5

hdisk0 blv=hd5

hdisk0 blv=hd5

So at this
point, I’d created a second instance of AIX running 7.1. My current version of
(running) AIX was AIX 6.1. All I had to do now was reboot the LPAR and let it
restart as an AIX 7.1 system.

root@aix6 /# oslevel -s

6100-01-05-0920

root@aix6 / # shutdown –Fr

The LPAR
rebooted successfully and I found I was now running AIX 7.1, just as I’d hoped.

aix6[/] > oslevel -s

7100-00-01-1037

If I wanted
to go back to AIX 6.1, I would change my bootlist setting again and restart the
LPAR.

Now that
I’ve actually tried this method of migration, I’m not sure I’d actually use it
in its current form.

Although
the migration keeps my hostname and IP address, the file systems are not shared
between instances. Most of the target systems configuration is not retained.
For example, any user accounts I create on my AIX 6.1 system would also need to
be created on the existing AIX.7.1 system which I used to create the AIX 7.1
mksysb image. It reminds me a little of a preservation install.